Arapahoe House, Colorado's largest provider of alcohol and other drug treatment services, proposes to demonstrate and evaluate Connections, a dyadic case management, integrated mental health and substance abuse treatment program for homeless individuals who are dually diagnosed. Connections uses two case managers, one with a background in substance abuse treatment and one with a background in mental health treatment, as the cornerstone of its intervention. This case manager dyad is first involved in outreach and engagement, including direct street outreach. When clients indicate readiness to begin treatment, they immediately enroll them into the program and admit them into Arapahoe House's residential program for stabilization, assessment, and development of an individualized treatment plan. Case managers link clients to a wide range of health and social services, including housing and the specialized dual- diagnosis treatment offered by Arapahoe House.Throughout client involvement with the program, the dyad helps build client skills in managing dual disorders through extensive modeling and advocacy. Long-term follow-up and support is also provided. The evaluation plan will use a non- randomized, quasi-experimental design. The primary goals are to: (1)compare the effectiveness of the Connections program with a traditional service system approach; (2) measure the fidelity between the Connections logic model and actual services delivery; and (3) determine whether specific elements of the program produce specific, theoretically linked, client outcomes. A total of 200 clients entering Arapahoe House will be assigned to one of two groups: the Connections program or a traditional treatment approach. Differences in the control group intervention will include: lack of outreach and engagement (the control group will be identified from the detoxification centers); lack of formal case management; standard course of treatment not geared to the special needs of the dually diagnosed; and referral (but not linkage and advocacy) to outside agencies for other services.